Test tube rack



FIG. 1 is a perspective view of a test tube rack showing my new design; and,

FIG. 2 is a top view thereof.

My test tube rack is characterized by columns positioned at the corners of the test tube positions, said columns in the interior of the rack having four concave sides, columns on the periphery of the rack having two concave sides and one flat side, columns at the four corners of the rack having one concave side and two flat sides, and each test tube position having a circular opening in its base. 

The ornamental design for a test tube rack, as shown and described. 